AliasSetTracker.cpp revision 794fd75c67a2cdc128d67342c6d88a504d186896
1//===- AliasSetTracker.cpp - Alias Sets Tracker implementation-------------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file was developed by the LLVM research group and is distributed under 6// the University of Illinois Open Source License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file implements the AliasSetTracker and AliasSet classes. 11// 12//===----------------------------------------------------------------------===// 13 14#include "llvm/Analysis/AliasSetTracker.h" 15#include "llvm/Analysis/AliasAnalysis.h" 16#include "llvm/Instructions.h" 17#include "llvm/Pass.h" 18#include "llvm/Type.h" 19#include "llvm/Target/TargetData.h" 20#include "llvm/Assembly/Writer.h" 21#include "llvm/Support/Compiler.h" 22#include "llvm/Support/InstIterator.h" 23#include "llvm/Support/Streams.h" 24using namespace llvm; 25 26/// mergeSetIn - Merge the specified alias set into this alias set. 27/// 28void AliasSet::mergeSetIn(AliasSet &AS, AliasSetTracker &AST) { 29 assert(!AS.Forward && "Alias set is already forwarding!"); 30 assert(!Forward && "This set is a forwarding set!!"); 31 32 // Update the alias and access types of this set... 33 AccessTy |= AS.AccessTy; 34 AliasTy |= AS.AliasTy; 35 36 if (AliasTy == MustAlias) { 37 // Check that these two merged sets really are must aliases. Since both 38 // used to be must-alias sets, we can just check any pointer from each set 39 // for aliasing. 40 AliasAnalysis &AA = AST.getAliasAnalysis(); 41 HashNodePair *L = getSomePointer(); 42 HashNodePair *R = AS.getSomePointer(); 43 44 // If the pointers are not a must-alias pair, this set becomes a may alias. 45 if (AA.alias(L->first, L->second.getSize(), R->first, R->second.getSize()) 46 != AliasAnalysis::MustAlias) 47 AliasTy = MayAlias; 48 } 49 50 if (CallSites.empty()) { // Merge call sites... 51 if (!AS.CallSites.empty()) 52 std::swap(CallSites, AS.CallSites); 53 } else if (!AS.CallSites.empty()) { 54 CallSites.insert(CallSites.end(), AS.CallSites.begin(), AS.CallSites.end()); 55 AS.CallSites.clear(); 56 } 57 58 AS.Forward = this; // Forward across AS now... 59 addRef(); // AS is now pointing to us... 60 61 // Merge the list of constituent pointers... 62 if (AS.PtrList) { 63 *PtrListEnd = AS.PtrList; 64 AS.PtrList->second.setPrevInList(PtrListEnd); 65 PtrListEnd = AS.PtrListEnd; 66 67 AS.PtrList = 0; 68 AS.PtrListEnd = &AS.PtrList; 69 assert(*AS.PtrListEnd == 0 && "End of list is not null?"); 70 } 71} 72 73void AliasSetTracker::removeAliasSet(AliasSet *AS) { 74 if (AliasSet *Fwd = AS->Forward) { 75 Fwd->dropRef(*this); 76 AS->Forward = 0; 77 } 78 AliasSets.erase(AS); 79} 80 81void AliasSet::removeFromTracker(AliasSetTracker &AST) { 82 assert(RefCount == 0 && "Cannot remove non-dead alias set from tracker!"); 83 AST.removeAliasSet(this); 84} 85 86void AliasSet::addPointer(AliasSetTracker &AST, HashNodePair &Entry, 87 unsigned Size, bool KnownMustAlias) { 88 assert(!Entry.second.hasAliasSet() && "Entry already in set!"); 89 90 // Check to see if we have to downgrade to _may_ alias. 91 if (isMustAlias() && !KnownMustAlias) 92 if (HashNodePair *P = getSomePointer()) { 93 AliasAnalysis &AA = AST.getAliasAnalysis(); 94 AliasAnalysis::AliasResult Result = 95 AA.alias(P->first, P->second.getSize(), Entry.first, Size); 96 if (Result == AliasAnalysis::MayAlias) 97 AliasTy = MayAlias; 98 else // First entry of must alias must have maximum size! 99 P->second.updateSize(Size); 100 assert(Result != AliasAnalysis::NoAlias && "Cannot be part of must set!"); 101 } 102 103 Entry.second.setAliasSet(this); 104 Entry.second.updateSize(Size); 105 106 // Add it to the end of the list... 107 assert(*PtrListEnd == 0 && "End of list is not null?"); 108 *PtrListEnd = &Entry; 109 PtrListEnd = Entry.second.setPrevInList(PtrListEnd); 110 assert(*PtrListEnd == 0 && "End of list is not null?"); 111 addRef(); // Entry points to alias set... 112} 113 114void AliasSet::addCallSite(CallSite CS, AliasAnalysis &AA) { 115 CallSites.push_back(CS); 116 117 if (Function *F = CS.getCalledFunction()) { 118 AliasAnalysis::ModRefBehavior Behavior = AA.getModRefBehavior(F, CS); 119 if (Behavior == AliasAnalysis::DoesNotAccessMemory) 120 return; 121 else if (Behavior == AliasAnalysis::OnlyReadsMemory) { 122 AliasTy = MayAlias; 123 AccessTy |= Refs; 124 return; 125 } 126 } 127 128 // FIXME: This should use mod/ref information to make this not suck so bad 129 AliasTy = MayAlias; 130 AccessTy = ModRef; 131} 132 133/// aliasesPointer - Return true if the specified pointer "may" (or must) 134/// alias one of the members in the set. 135/// 136bool AliasSet::aliasesPointer(const Value *Ptr, unsigned Size, 137 AliasAnalysis &AA) const { 138 if (AliasTy == MustAlias) { 139 assert(CallSites.empty() && "Illegal must alias set!"); 140 141 // If this is a set of MustAliases, only check to see if the pointer aliases 142 // SOME value in the set... 143 HashNodePair *SomePtr = getSomePointer(); 144 assert(SomePtr && "Empty must-alias set??"); 145 return AA.alias(SomePtr->first, SomePtr->second.getSize(), Ptr, Size); 146 } 147 148 // If this is a may-alias set, we have to check all of the pointers in the set 149 // to be sure it doesn't alias the set... 150 for (iterator I = begin(), E = end(); I != E; ++I) 151 if (AA.alias(Ptr, Size, I.getPointer(), I.getSize())) 152 return true; 153 154 // Check the call sites list and invoke list... 155 if (!CallSites.empty()) { 156 if (AA.hasNoModRefInfoForCalls()) 157 return true; 158 159 for (unsigned i = 0, e = CallSites.size(); i != e; ++i) 160 if (AA.getModRefInfo(CallSites[i], const_cast<Value*>(Ptr), Size) 161 != AliasAnalysis::NoModRef) 162 return true; 163 } 164 165 return false; 166} 167 168bool AliasSet::aliasesCallSite(CallSite CS, AliasAnalysis &AA) const { 169 if (Function *F = CS.getCalledFunction()) 170 if (AA.doesNotAccessMemory(F)) 171 return false; 172 173 if (AA.hasNoModRefInfoForCalls()) 174 return true; 175 176 for (unsigned i = 0, e = CallSites.size(); i != e; ++i) 177 if (AA.getModRefInfo(CallSites[i], CS) != AliasAnalysis::NoModRef || 178 AA.getModRefInfo(CS, CallSites[i]) != AliasAnalysis::NoModRef) 179 return true; 180 181 for (iterator I = begin(), E = end(); I != E; ++I) 182 if (AA.getModRefInfo(CS, I.getPointer(), I.getSize()) != 183 AliasAnalysis::NoModRef) 184 return true; 185 186 return false; 187} 188 189 190/// findAliasSetForPointer - Given a pointer, find the one alias set to put the 191/// instruction referring to the pointer into. If there are multiple alias sets 192/// that may alias the pointer, merge them together and return the unified set. 193/// 194AliasSet *AliasSetTracker::findAliasSetForPointer(const Value *Ptr, 195 unsigned Size) { 196 AliasSet *FoundSet = 0; 197 for (iterator I = begin(), E = end(); I != E; ++I) 198 if (!I->Forward && I->aliasesPointer(Ptr, Size, AA)) { 199 if (FoundSet == 0) { // If this is the first alias set ptr can go into. 200 FoundSet = I; // Remember it. 201 } else { // Otherwise, we must merge the sets. 202 FoundSet->mergeSetIn(*I, *this); // Merge in contents. 203 } 204 } 205 206 return FoundSet; 207} 208 209/// containsPointer - Return true if the specified location is represented by 210/// this alias set, false otherwise. This does not modify the AST object or 211/// alias sets. 212bool AliasSetTracker::containsPointer(Value *Ptr, unsigned Size) const { 213 for (const_iterator I = begin(), E = end(); I != E; ++I) 214 if (!I->Forward && I->aliasesPointer(Ptr, Size, AA)) 215 return true; 216 return false; 217} 218 219 220 221AliasSet *AliasSetTracker::findAliasSetForCallSite(CallSite CS) { 222 AliasSet *FoundSet = 0; 223 for (iterator I = begin(), E = end(); I != E; ++I) 224 if (!I->Forward && I->aliasesCallSite(CS, AA)) { 225 if (FoundSet == 0) { // If this is the first alias set ptr can go into. 226 FoundSet = I; // Remember it. 227 } else if (!I->Forward) { // Otherwise, we must merge the sets. 228 FoundSet->mergeSetIn(*I, *this); // Merge in contents. 229 } 230 } 231 232 return FoundSet; 233} 234 235 236 237 238/// getAliasSetForPointer - Return the alias set that the specified pointer 239/// lives in... 240AliasSet &AliasSetTracker::getAliasSetForPointer(Value *Pointer, unsigned Size, 241 bool *New) { 242 AliasSet::HashNodePair &Entry = getEntryFor(Pointer); 243 244 // Check to see if the pointer is already known... 245 if (Entry.second.hasAliasSet()) { 246 Entry.second.updateSize(Size); 247 // Return the set! 248 return *Entry.second.getAliasSet(*this)->getForwardedTarget(*this); 249 } else if (AliasSet *AS = findAliasSetForPointer(Pointer, Size)) { 250 // Add it to the alias set it aliases... 251 AS->addPointer(*this, Entry, Size); 252 return *AS; 253 } else { 254 if (New) *New = true; 255 // Otherwise create a new alias set to hold the loaded pointer... 256 AliasSets.push_back(new AliasSet()); 257 AliasSets.back().addPointer(*this, Entry, Size); 258 return AliasSets.back(); 259 } 260} 261 262bool AliasSetTracker::add(Value *Ptr, unsigned Size) { 263 bool NewPtr; 264 addPointer(Ptr, Size, AliasSet::NoModRef, NewPtr); 265 return NewPtr; 266} 267 268 269bool AliasSetTracker::add(LoadInst *LI) { 270 bool NewPtr; 271 AliasSet &AS = addPointer(LI->getOperand(0), 272 AA.getTargetData().getTypeSize(LI->getType()), 273 AliasSet::Refs, NewPtr); 274 if (LI->isVolatile()) AS.setVolatile(); 275 return NewPtr; 276} 277 278bool AliasSetTracker::add(StoreInst *SI) { 279 bool NewPtr; 280 Value *Val = SI->getOperand(0); 281 AliasSet &AS = addPointer(SI->getOperand(1), 282 AA.getTargetData().getTypeSize(Val->getType()), 283 AliasSet::Mods, NewPtr); 284 if (SI->isVolatile()) AS.setVolatile(); 285 return NewPtr; 286} 287 288bool AliasSetTracker::add(FreeInst *FI) { 289 bool NewPtr; 290 AliasSet &AS = addPointer(FI->getOperand(0), ~0, 291 AliasSet::Mods, NewPtr); 292 293 // Free operations are volatile ops (cannot be moved). 294 AS.setVolatile(); 295 return NewPtr; 296} 297 298 299bool AliasSetTracker::add(CallSite CS) { 300 if (Function *F = CS.getCalledFunction()) 301 if (AA.doesNotAccessMemory(F)) 302 return true; // doesn't alias anything 303 304 AliasSet *AS = findAliasSetForCallSite(CS); 305 if (!AS) { 306 AliasSets.push_back(new AliasSet()); 307 AS = &AliasSets.back(); 308 AS->addCallSite(CS, AA); 309 return true; 310 } else { 311 AS->addCallSite(CS, AA); 312 return false; 313 } 314} 315 316bool AliasSetTracker::add(Instruction *I) { 317 // Dispatch to one of the other add methods... 318 if (LoadInst *LI = dyn_cast<LoadInst>(I)) 319 return add(LI); 320 else if (StoreInst *SI = dyn_cast<StoreInst>(I)) 321 return add(SI); 322 else if (CallInst *CI = dyn_cast<CallInst>(I)) 323 return add(CI); 324 else if (InvokeInst *II = dyn_cast<InvokeInst>(I)) 325 return add(II); 326 else if (FreeInst *FI = dyn_cast<FreeInst>(I)) 327 return add(FI); 328 return true; 329} 330 331void AliasSetTracker::add(BasicBlock &BB) { 332 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I) 333 add(I); 334} 335 336void AliasSetTracker::add(const AliasSetTracker &AST) { 337 assert(&AA == &AST.AA && 338 "Merging AliasSetTracker objects with different Alias Analyses!"); 339 340 // Loop over all of the alias sets in AST, adding the pointers contained 341 // therein into the current alias sets. This can cause alias sets to be 342 // merged together in the current AST. 343 for (const_iterator I = AST.begin(), E = AST.end(); I != E; ++I) 344 if (!I->Forward) { // Ignore forwarding alias sets 345 AliasSet &AS = const_cast<AliasSet&>(*I); 346 347 // If there are any call sites in the alias set, add them to this AST. 348 for (unsigned i = 0, e = AS.CallSites.size(); i != e; ++i) 349 add(AS.CallSites[i]); 350 351 // Loop over all of the pointers in this alias set... 352 AliasSet::iterator I = AS.begin(), E = AS.end(); 353 bool X; 354 for (; I != E; ++I) 355 addPointer(I.getPointer(), I.getSize(), 356 (AliasSet::AccessType)AS.AccessTy, X); 357 } 358} 359 360/// remove - Remove the specified (potentially non-empty) alias set from the 361/// tracker. 362void AliasSetTracker::remove(AliasSet &AS) { 363 // Drop all call sites. 364 AS.CallSites.clear(); 365 366 // Clear the alias set. 367 unsigned NumRefs = 0; 368 while (!AS.empty()) { 369 AliasSet::HashNodePair *P = AS.PtrList; 370 371 // Unlink from the list of values. 372 P->second.removeFromList(); 373 374 // Remember how many references need to be dropped. 375 ++NumRefs; 376 377 // Finally, remove the entry. 378 Value *Remove = P->first; // Take a copy because it is invalid to pass 379 PointerMap.erase(Remove); // a reference to the data being erased. 380 } 381 382 // Stop using the alias set, removing it. 383 AS.RefCount -= NumRefs; 384 if (AS.RefCount == 0) 385 AS.removeFromTracker(*this); 386} 387 388bool AliasSetTracker::remove(Value *Ptr, unsigned Size) { 389 AliasSet *AS = findAliasSetForPointer(Ptr, Size); 390 if (!AS) return false; 391 remove(*AS); 392 return true; 393} 394 395bool AliasSetTracker::remove(LoadInst *LI) { 396 unsigned Size = AA.getTargetData().getTypeSize(LI->getType()); 397 AliasSet *AS = findAliasSetForPointer(LI->getOperand(0), Size); 398 if (!AS) return false; 399 remove(*AS); 400 return true; 401} 402 403bool AliasSetTracker::remove(StoreInst *SI) { 404 unsigned Size = AA.getTargetData().getTypeSize(SI->getOperand(0)->getType()); 405 AliasSet *AS = findAliasSetForPointer(SI->getOperand(1), Size); 406 if (!AS) return false; 407 remove(*AS); 408 return true; 409} 410 411bool AliasSetTracker::remove(FreeInst *FI) { 412 AliasSet *AS = findAliasSetForPointer(FI->getOperand(0), ~0); 413 if (!AS) return false; 414 remove(*AS); 415 return true; 416} 417 418bool AliasSetTracker::remove(CallSite CS) { 419 if (Function *F = CS.getCalledFunction()) 420 if (AA.doesNotAccessMemory(F)) 421 return false; // doesn't alias anything 422 423 AliasSet *AS = findAliasSetForCallSite(CS); 424 if (!AS) return false; 425 remove(*AS); 426 return true; 427} 428 429bool AliasSetTracker::remove(Instruction *I) { 430 // Dispatch to one of the other remove methods... 431 if (LoadInst *LI = dyn_cast<LoadInst>(I)) 432 return remove(LI); 433 else if (StoreInst *SI = dyn_cast<StoreInst>(I)) 434 return remove(SI); 435 else if (CallInst *CI = dyn_cast<CallInst>(I)) 436 return remove(CI); 437 else if (FreeInst *FI = dyn_cast<FreeInst>(I)) 438 return remove(FI); 439 return true; 440} 441 442 443// deleteValue method - This method is used to remove a pointer value from the 444// AliasSetTracker entirely. It should be used when an instruction is deleted 445// from the program to update the AST. If you don't use this, you would have 446// dangling pointers to deleted instructions. 447// 448void AliasSetTracker::deleteValue(Value *PtrVal) { 449 // Notify the alias analysis implementation that this value is gone. 450 AA.deleteValue(PtrVal); 451 452 // If this is a call instruction, remove the callsite from the appropriate 453 // AliasSet. 454 CallSite CS = CallSite::get(PtrVal); 455 if (CS.getInstruction()) { 456 Function *F = CS.getCalledFunction(); 457 if (!F || !AA.doesNotAccessMemory(F)) { 458 if (AliasSet *AS = findAliasSetForCallSite(CS)) 459 AS->removeCallSite(CS); 460 } 461 } 462 463 // First, look up the PointerRec for this pointer. 464 hash_map<Value*, AliasSet::PointerRec>::iterator I = PointerMap.find(PtrVal); 465 if (I == PointerMap.end()) return; // Noop 466 467 // If we found one, remove the pointer from the alias set it is in. 468 AliasSet::HashNodePair &PtrValEnt = *I; 469 AliasSet *AS = PtrValEnt.second.getAliasSet(*this); 470 471 // Unlink from the list of values... 472 PtrValEnt.second.removeFromList(); 473 // Stop using the alias set 474 AS->dropRef(*this); 475 PointerMap.erase(I); 476} 477 478// copyValue - This method should be used whenever a preexisting value in the 479// program is copied or cloned, introducing a new value. Note that it is ok for 480// clients that use this method to introduce the same value multiple times: if 481// the tracker already knows about a value, it will ignore the request. 482// 483void AliasSetTracker::copyValue(Value *From, Value *To) { 484 // Notify the alias analysis implementation that this value is copied. 485 AA.copyValue(From, To); 486 487 // First, look up the PointerRec for this pointer. 488 hash_map<Value*, AliasSet::PointerRec>::iterator I = PointerMap.find(From); 489 if (I == PointerMap.end() || !I->second.hasAliasSet()) 490 return; // Noop 491 492 AliasSet::HashNodePair &Entry = getEntryFor(To); 493 if (Entry.second.hasAliasSet()) return; // Already in the tracker! 494 495 // Add it to the alias set it aliases... 496 AliasSet *AS = I->second.getAliasSet(*this); 497 AS->addPointer(*this, Entry, I->second.getSize(), true); 498} 499 500 501 502//===----------------------------------------------------------------------===// 503// AliasSet/AliasSetTracker Printing Support 504//===----------------------------------------------------------------------===// 505 506void AliasSet::print(std::ostream &OS) const { 507 OS << " AliasSet[" << (void*)this << "," << RefCount << "] "; 508 OS << (AliasTy == MustAlias ? "must" : "may ") << " alias, "; 509 switch (AccessTy) { 510 case NoModRef: OS << "No access "; break; 511 case Refs : OS << "Ref "; break; 512 case Mods : OS << "Mod "; break; 513 case ModRef : OS << "Mod/Ref "; break; 514 default: assert(0 && "Bad value for AccessTy!"); 515 } 516 if (isVolatile()) OS << "[volatile] "; 517 if (Forward) 518 OS << " forwarding to " << (void*)Forward; 519 520 521 if (begin() != end()) { 522 OS << "Pointers: "; 523 for (iterator I = begin(), E = end(); I != E; ++I) { 524 if (I != begin()) OS << ", "; 525 WriteAsOperand(OS << "(", I.getPointer()); 526 OS << ", " << I.getSize() << ")"; 527 } 528 } 529 if (!CallSites.empty()) { 530 OS << "\n " << CallSites.size() << " Call Sites: "; 531 for (unsigned i = 0, e = CallSites.size(); i != e; ++i) { 532 if (i) OS << ", "; 533 WriteAsOperand(OS, CallSites[i].getCalledValue()); 534 } 535 } 536 OS << "\n"; 537} 538 539void AliasSetTracker::print(std::ostream &OS) const { 540 OS << "Alias Set Tracker: " << AliasSets.size() << " alias sets for " 541 << PointerMap.size() << " pointer values.\n"; 542 for (const_iterator I = begin(), E = end(); I != E; ++I) 543 I->print(OS); 544 OS << "\n"; 545} 546 547void AliasSet::dump() const { print (cerr); } 548void AliasSetTracker::dump() const { print(cerr); } 549 550//===----------------------------------------------------------------------===// 551// AliasSetPrinter Pass 552//===----------------------------------------------------------------------===// 553 554namespace { 555 class VISIBILITY_HIDDEN AliasSetPrinter : public FunctionPass { 556 AliasSetTracker *Tracker; 557 public: 558 static const int ID; // Pass identifcation, replacement for typeid 559 AliasSetPrinter() : FunctionPass((intptr_t)&ID) {} 560 561 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 562 AU.setPreservesAll(); 563 AU.addRequired<AliasAnalysis>(); 564 } 565 566 virtual bool runOnFunction(Function &F) { 567 Tracker = new AliasSetTracker(getAnalysis<AliasAnalysis>()); 568 569 for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) 570 Tracker->add(&*I); 571 Tracker->print(cerr); 572 delete Tracker; 573 return false; 574 } 575 }; 576 const int AliasSetPrinter::ID = 0; 577 RegisterPass<AliasSetPrinter> X("print-alias-sets", "Alias Set Printer"); 578} 579